Fuel pumps are commonly used to transfer fuel to an injection system for an engine. It is common for a fuel pump to be driven by a type of motor, such as an electric motor. The operation of the fuel pump and motor are typically controlled by some type of closed-loop feedback system, where pressure is monitored, and the speed of the pump is adjusted based on a comparison of the measured pressure to the desired pressure. These types of closed-loop feedback control systems require a pressure sensor to monitor the pressure. The type of pressure sensor required for a closed-loop feedback system is costly and adds components to the system.
Other attempts have been made to control a fuel pump and motor by using an open-loop control system. An open-loop control system includes a control map which includes various speeds and flow rates which correspond to each speed, the pump operates at a particular speed to generate the correct flow. An open-loop system for a fuel pump does not provide a measurement of pressure that is used for comparison to a desired pressure. There are several speeds used to provide different flow rates, and the operation of the pump is changed to correspond to a desired flow rate. Known mapped control systems (such as open-loop control systems) exhibit a high uncertainty with regard to the real pressure and may not always take advantage of full potential energy savings, since under certain conditions high fitting pressure adversely affects the energy balance.
Accordingly, there exists a need for a closed-loop control system for a fuel pump which does not require a pressure sensor, and is more accurate than an open-loop control system.